The invention relates to a sensor for measuring fluid flow speeds.
Various design options for sensors used to measure fluid flow speeds are disclosed in an G. Stemme, “Micro Fluid Sensors and Actuators,” Proceedings for the 6th International Symposium on Micro Machine and Human Science, pages 45-52, 1995. Among other things, it is described how a conductive track, installed on a thin membrane, is maintained at a constant temperature with the aid of an electrical current and the energy for maintaining the temperature is used for measuring the flow speed. More detailed descriptions of how to operate such a sensor can be found in the book STRÖMUNGS—UND DURCHFLUSSMESSTECHNIK [Flow and Flow-Through Measuring Technology], by Otto Fiedler, pages 159-163, House of Oldenbourg, publishers, 1992.
The article by W. K. Schomburg et al titled “AMANDA—Surface Micromachining, Molding, and Diaphragm Transfer,” published in the magazine Sensors and Actuators A, Volume 76, pages 343 to 348, describes a sensor for measuring flow speeds by measuring the pressure drop above a capillary with a pressure sensor. The pressure drop is proportional to the flow speed and can therefore be used for measuring the flow speed. The pressure sensor used in this sensor comprises strain gauges that are installed on a thin membrane.
The disadvantage of both above-described methods for measuring flow speeds is that forces acting from the outside upon the sensor housing, as well as thermal strains of the housing itself as a result of changes in the environmental temperature, can strain the conductive track so that its electrical resistance changes, thus simulating a changed flow speed.